Waterfast ink composition for printers

ABSTRACT

Liquid inks are disclosed that fulfill United States Postal Service requirements for automation compatibility, while being able to be used in an ink jet printer. The inks of this invention may be read by current United States Postal Service equipment. The inks are waterfast, having improved print quality. The formulations are based on water cosolvent solutions of soluble fluorescent or non fluorescent toners to which toning dyes and non ionic surfactants are added.

CROSS REFERENCE TO RELATED APPLICATIONS

Reference is made to commonly assigned copending patent application Ser.No. 08/570,140 Docket No. E-407, filed herewith entitled "FluorescentRed And Magenta Waterfast Ink Jet Inks" in the names of Judith Auslanderand Shunichi Higashiyama.

FIELD OF THE INVENTION

The invention relates generally to inks, and more particularly to inksthat may be used in an Ink jet printer.

BACKGROUND OF THE INVENTION

Inks have been used in Europe and elsewhere in postage meters orfranking machines for imprinting postal indicia. The image obtained withthe red inks for the above application has to be permanent, i.e. goodwater fastness, smear fastness and light fastness i.e., greater than95%. Also, the images on various substrates have to show enhancedcontrast properties.

Postal indicia or franking machines have been developed that use digitalprinting technology to permit the use of variable information on thepostal indicia and have more accurate printing and indicia printquality. The enhanced print quality will enable the postal indicia to beeasily read by optical character recognition equipment, bar code readersand other types of technologies.

The introduction of digital printing and franking is conditioned by theexistence of inks that are suitable for franking, but at the same timeare functional with the specific ink jet technology. Currently, theclosest inks that meet the above criteria are the magenta inks that areused in ink jet printers. The aforementioned magenta inks areaccidentally fluorescent, since the choice of the magenta dyes is verynarrow and the most brilliant available magenta dyes are fluorescent.One of the few available water soluble magenta dyes is the Acid Red 52.The Acid Red 52 has satisfactory solubility in water but a very lowwater fastness. Thus, a disadvantage of the magenta Acid Red 52 ink isthat the ink bleeds under water exposure. Another disadvantage of usingcurrent magenta inks is that prints obtained with these inks offset onthe back of neighboring envelopes when exposed to water.

Another disadvantage of prior art piezoelectric ink jet inks which arewater fast is that the inks use different organic solvents instead ofwater. Various organic solvents, such as tripropylene glycol methylether or other glycol ethers, are used to improve the water fastness.The reason for the above is that the solvents dissolve or dispersecolorants that are insoluble in water. Due to safety and compatibilityrequirements, with various plastic materials used in ink jet printheads, water is nevertheless desirable as the main solvent. The reasonwhy water is desirable as a solvent when plastic materials are used isthat water is much less aggressive than the organic solvents. The widelyused plastic materials for ink jet printer parts are inker foam,cartridge material, glue, printer base, etc. The above parts may be madefrom Acrylonitrile styrene (AS), Polymethyl metaacrylate (PMMA), andAcrylonitrile butadiene styrene (ABS). Therefore, the disadvantage ofusing organic solvents is that they attack plastic materials. Onceplastic materials are attacked, the printer would not work properly. Awater based ink is desirable as the main solvent since it's inert tomost ink jet printer components.

The ink that is going to be used in an ink jet printer, must havecertain physical properties, such as a certain viscosity and a specifiedsurface tension. The viscosity of the liquid inks used in currentpiezoelectric ink jet printers is 1.5-20 cps and in the thermal ink jetprinter is very low (1-5 cps). The desirable surface tension of liquidink jet printer inks should be between 30-45 dynes/cm.

A disadvantage of current water based ink jet inks is that the ink has atendency to dry in the nozzles of the printer, during operation of theprinter and between operations of the printer.

One of the properties of an ink that is used in an ink jet printer isthe decap time, which is the length of time over which an ink remainsfluid in a nozzle opening when exposed to air and capable of firing adrop. Precipitation of the solid in the ink is what causes failure orcoagulation in the ink and is often due to evaporation of the solventcausing precipitation or crystallization of a solid at the air/liquidsurface.

Another disadvantage of the water based inks is that they have to use"naked" (pure) dyes without resins in order to achieve good solubility.The dyes should be preferably direct, acid, basic or reactive.

If the solubility of the colorant material in the solvent is not goodenough, the drops stability, and the print quality are poor. The longterm solubility which affects the shelf life depends on the colorantsolubility in the solvent in various environmental conditions oftemperature and humidity. The dyes that exhibit good water solubilitysuffer from deficiency in water fastness and smear fastness on thegenerated prints. The foregoing occurs because of the printsredisolution in water.

Another disadvantage of dye based inks is that they produce prints withhigh edge roughness and poorly defined characters which is also calledfeathering. The foregoing disadvantage is more apparent at lowerresolutions such as 240 dpi, where there is less overlap between thedots.

Therefore, pigments which are insoluble in water are a preferredalternative to dyes provided that pigments dispersions can be madestable to sedimentation and gelling.

The problem of using pigments is that they exhibit fragile equilibriumin dispersion. The dispersions are easily destabilized by changes intemperature, humidity and impurities.

Other typical liquid ink properties are the inks ability to penetratepaper and to dry fast by absorption. Another problem with fastpenetrating inks is that the optical density decreases with the inkpenetration. The above effect has to be compensated for in order toachieve good print quality. Good print quality may be achieved by usingdyes with high absorbance values.

Another problem of prior art inks is that they do not give consistentprint quality on a large variety of substrates. Postage meter inks haveto be used on a large variety of paper envelopes. The components of thepaper can have adverse effects on print quality and on the opticaldensity of the prints. The wax based inks such as hot melt ink do notinteract with the paper in the same manner as the liquid inks.Therefore, there is a need for a liquid franking ink that will haveconsistent fluorescence and optical density on a large variety ofenvelopes, while interacting with the paper.

Another problem of prior art waterfast inks is that the components ofthe ink that are responsible for waterfastness have difficulty inachieving long term solubility. The large temperature variationencountered by the ink during normal operating conditions maydestabilize the equilibrium of the ink causing settling of particles inthe ink, which may cause clogging of the nozzles of the ink jet printer.

SUMMARY OF THE INVENTION

This invention overcomes the disadvantages of the prior art by providinga ink jet ink that produces better print quality and image permanence,while fulfilling the United States Postal Service requirements forautomation compatibility. The inks of this invention may be read bycurrent Postal Service optical character recognition equipment and/orbar code reading systems. The inks of this invention are safe for use inan office environment. The inks also are non toxic and inert to therange of materials used in the print heads of current ink jet printers.Some of the materials in ink jet print heads are polycarbonate (PC),Polystylene (PS) and Polyphenyleneoxide. One of the advantages of theinks of this invention is that the inks provide a permanent image (waterand light fast) on a large variety of substrates.

The inks disclosed herein are based on solutions of soluble toners inwater/cosolvent systems. The prints obtained with the inks of thisinvention are resistant to water exposure either by drainage or bydipping in water. Also the inks do not offset while exposed to water andwhen they are in contact under pressure with other pieces of paper. Theinks of this invention are based on water as a main solvent (greaterthan 35%) and other cosolvents which are water soluble. The watersoluble organic solvents serve to prevent clogging at the nozzle throughmoisture retention (hygroscopicity) and at the same time improve thestability of the ink. The other role of the organic solvents is todecrease the surface tension of the ink and increase the paper spreadingand drying time. The last role of the cosolvent is to improve thesolubility of the toner for the range of various types of tonerscompatible with the vehicle. The toner is a solid solution of a dye in aresin that is soluble or partially soluble in water, or in a watersoluble organic solvent.

The water soluble solvents have to be polar. Solvent polarity is theover-all solvation ability of a solvent which in turn is determined bythe sum of all the molecular properties responsible for the interactionsbetween the solvent and the solute. These intermolecular forces are:columbic, directional, inductive, dispersion, charge transfer andhydrogen bonding. The solvent polarity is defined quantitatively byphysical parameters: ε the dielectric constant and μ the permanentdipole moment. The dielectric constant describes the ability of asolvent to separate electrical charges and orient its dipolar molecules.The permanent dipole moment of a molecule is given by the product of thecharges of the dipole units and the distance separating the two dipolecharges. Another empirical parameter used for defining over all solventpolarity is the standard absorption of organic compounds (E_(t))determined by the λ_(max) of organic compounds in different solutions.Examples of the water-soluble organic solvents with low vapor pressureare: glycerol, ethylene glycol, diethylene glycol, triethylene glycol,propylene glycol, dipropylene glycol, hexylene glycol, polyethylene andpolypropylene glycol.

The water soluble organic cosolvents may be used alone or in combinationof two or more of them. The cosolvents used in the ink formulations haveto be totally miscible with water, good solvents for a broad range ofpolar resins, nonvolatile (vapor pressure at room temperature less than0.1 mm/Hg) and inert to the commonly used plastic materials. Further, itis preferred for the ink composition of the present invention to furthercontain highly volatile monhydric alcohols such as ethanol, propanol andisopropanol, from the viewpoint of improving the quick drying and fixingof prints.

In the ink composition according to the present invention, when thewater soluble organic solvents are used alone, the Hildebrand solubilityparameter (SP value) of the water soluble organic solvent used ispreferably 12 cal/cm³ or more. Also, when the water soluble organicsolvents are used in combination of two or more of them, the SP value ofthe mixed organic solvent is preferably 12 cal/cm³ or more. The SP valueof the mixed solvent can be determined from the following equation.##EQU1## wherein δ represents an SP value of each solvent, X representsa molar fraction of each solvent in the mixed solvent, V represents amolar volume of each solvent and n is a subscript representing the kindof the solvent and an integer of 2 or more. Other solvents that can beused are: 2-pyrrolidone, N-methyl pyrrolidone, sulfolane, gammabutyrlactone, etc.

The hygroscopic characteristics of the organic cosolvents used in theink formulations prevent drying at the ink jet nozzles and thereforeimprove the ink reliability in the print head. An additional advantageof the inks of this invention is the high water and cosolvent solubilityof the soluble toner which improves the shelf life of the ink. Thegeneral characteristics of these solvents as expressed in partial Hansensolubility parameters (δ.sub.δ (dispersion), δ_(p) (polar), δ_(h)(hydrogen bonding)) are as follows. For the category of solvents withlow dispersion solubility parameter δ.sub.δ (7-8.3) they should haveδ_(h) >8.0, δ_(p) >5.0. Examples are: diethylene glycol (δ.sub.δ of7.9), triethylene glycol (δ.sub.δ of 7.8). From the category of highδ.sub.δ (8.4-10.0) they should have δ_(h) >5.0, δ_(p) of 8.0-8.7. Someexamples of the foregoing are: 2-pyrrolidone, N-methyl pyrrolidone,suffolane, gamma butyrlactone, etc. The water soluble organic solventindividually or in solution does not exceed a viscosity of 20 cps.

The increased solubility of the colorant of the inks of this inventionin water or in the solvent system used, makes this ink very efficient;and provides efficient jetting ability. Hence, good print quality isobtained. To the water cosolvent solution which also may be a cosolventmixture a glycol ether is added. The glycol ether serves as a dyestabilizer, wetting and as a coupling agent. The glycol ethers areintramolecularly hydrogen bonded. They can therefore act as bridgingsolvents and assume the polar or non polar nature of their surroundingenvironment. The glycol ethers may act as polar solvents with polarresins and with less polar resins the above glycol ethers may act as nonpolar solvents. Therefore, they serve to solubilize relatively non polarresins in water. Examples of glycol ethers are: diethylene glycol ethylether; triethylene glycol ethyl ether; diethylene glycol butyl ether;diethylene glycol propyl ether; and propylene glycol butyl ether. All ofthe glycol ethers should have a viscosity less than 20 cps. Another veryimportant role of the glycol ether is that they are strong penetrantsinto paper.

The ink formulation of this invention consists of an aqueous carriermedium, a "water like" organic polar solvent, "a water soluble toner"containing a dye encapsulated in a resin matrix and cosolvent penetrantssuch as propylene glycol butyl ether, diethylene glycol, or triethyleneglycol butyl ether.

In order to solubilize toners based upon acid resins non ionicsurfactants have to be added. The non ionic surfactants have HLB valuesfrom 8-15. The surfactants belong to the class of nonyl phenoxy poly(ethyleneoxy) ethoxylates or decyl and tridecyl alcohol ethoxylates.Other additives, such as dimethyl hydantoin can be used for good decapperformance. The resultant inks are water fast on a large variety ofsubstrates/envelopes. They are also non toxic and inert to most of thematerials used in the print head. These inks exhibit rapid drying, arestorage stable and give images having good print quality, andpermanence. In essence, the ink formulation of this invention is a watercosolvent based ink that uses toners that contain dyes encapsulated in aresin matrix instead of dyes. Hence, the major solvent of the inkformulation is water, while at the same time, the dye protected by theresin is not bleeding under water exposure and a water environment.Therefore, the resulting print is waterfast.

Water based inks may be formulated that contain between 30-60% waterwith additional cosolvents that are water soluble and water like, likeglycols, diethylene glycol, triethylene glycol, tetraethylene glycol(which have a relatively low viscosity) and/or other polar solvents,such as 2 pyrrolidone or N-methyl pyrrolidone or gammabutylactone orsulfolane may be used. All of the above solvents are nonvolatile,hygroscopic, and at the same time dissolve well in water causing anincrease in the viscosity. The above solvents have a high dipole momentwhich is greater than 2.3 but preferably greater than 3 and with highhydrogen bonding solubility parameters which are greater than 5. Thecombination of the toner, water, cosolvent, and peneterant have to beadjusted for a desired viscosity.

The aforementioned solvents have to comply with all government safetystandards that are defined by applicable statues and regulations.Therefore, a safe solvent may be defined as a solvent with, mild ormoderate skin and eye irritation index and a haft life lethal dosegreater than 1 g/kg.

Another property of the ink formulation is that the using of an additivelike a glycol ether such as propylene glycol, n- butyl ether ortriethylene glycol butyl ether improves the water fastness and the speedof penetration of the ink into the paper. The above solvents also have astrong effect on the dye stabilization. The water fastness is improvedby the fact that the penetrant helps the toner to sink deeper into thepaper fiber thus, protecting the dye from being released from the resin.

The use of toners i.e., dyes encapsulated in a resin results in aperformance soluble similar to a soluble dye in solution and as apigment on paper.

The solubility of the colorant has to be high enough so as not to causeproblems in the shelf life, or in the ejection stability. The desiredshelf life of more than one year is achieved by using very solubletoners like dimethyl hydantoin/formaldehyde or by adding non ionicsurfactants acid resins (polyester polyamide). The non ionic surfactantsbelong to tridecyl alcohol alkoylates or nonyl phenoxy poly(ethyleneoxy) ethanol with HLB between 8 and 13 at concentrations oftrace to 3%. At the same time, when the ink hits the paper, it has tobecome insoluble in water or in any other material that may come incontact with the paper, like coffee, bleaching agents or other liquidsthat can be exposed to a print.

After the toner is laid on the paper and after the evaporation of thesolvent, the properties of the toner are more similar to a pigment thanto a dye, because of the protection by the resin. The watersolubilization of the toner on the printed image is also hindered due tothe fact that the dye is protected by the resin. Therefore, by usingsoluble toners, a dual effect is obtained i.e., the functioning as a dyein the ink solution in the cartridge and print head and as a pigmentwhen printed on the paper. Other effects similar to pigmented inksinclude enhanced contrasts, high optical density, image permanence andsuperior edge definition. In addition to the toner/solvent mixtures"loose" dye is added to enhance the contrast. The dyes can belong tovarious categories such as: direct, acid and basic. Some examples are:C.I. Direct Yellow 86, C.I. Acid Yellow 210, C.I. Basic Yellow 40, C.I.Direct, C.I. Direct Yellow 142, Solvent Yellow 44, C.I. Basic Blue 7,C.I. Basic Blue 3, C.I. Basic Yellow 51, C.I. Basic Yellow 2 etc. Otherdyes like magenta, violet, blue or green may be added in smallconcentrations. The pure dye added to the ink is soluble in the solventmixture and belongs to the categories of acid, direct, basic or watersoluble toning dyes. Preferably the dyes used are basic. Theconcentration used is trace to 8.0 (wt. 90).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The formulation of the ink of the instant invention provides magenta orred inks that are capable of being used in an ink jet printer and areinert to materials used in the printer. Composition of the ink, inaccordance with the invention comprises: soluble toner or mixturethereof from 3-15%, water 35-55%, cosolvent which is a water solubleorganic solvent from 15-47% or a mixture thereof and Glycol Ether asadditive 3-15%. Other agents that can be used for solubilization or PHstabilization are low volatility alkali components, or acid componentsof food grade or for cosmetics. Specific preferred examples of thenonvolatile alkali components include alkanolamines, for examples, monoethanolamine, N-N-dimethylethanolamine, N-N-diethylethanolamine,diethanolamine, triethanolamine, N-N-butyldiethanolamine andtriisopropanolamine.

The ink composition of the invention is suitable employed with any inkjet printer for any drop on demand ink jet technology. However, it isparticularly useful in piezoelectric ink jet technology.

Soluble toner is defined as a solid solution of a dye in a polar resinmatrix or a soluble polar resin such as dimethyl hydantoin formaldehyde.The dye can be fluorescent or non fluorescent and can belong to variousdye groups, such as direct dyes, solvent dyes, acid dyes, or basic dyes.The concentration of the dye in the toner ranges from 1-8%. It iscontemplated that any of the dyes currently used in inks for ink jetprinters may be used as dyes in the ink formulation of this invention.The resin used to dissolve any of the dyes belong to the type triazineformaldehyde sulfonamide and can be either urea formaldehyde, melamineformaldehyde or benzoguanamine formaldehyde which are cross linked withpara toluene sulfonamide. Other resins that can be used arepolyester/polyamide. The above resins have a low molecular weight lessthan 6,000 and a high acid number (greater than 50). The weight averagemolecular weight (Mn) is preferably between 200 and 1000. An alternativeresin matrix is dimethyl hydantoin formaldehyde which has a good watersolubility.

The water soluble solvents that are used can belong to the group ofglycols, including propylene glycols, polypropylene glycols, ethyleneglycols, polyethylene glycols and glycerols. Any, of the glycol familiesof ethers and mixtures thereof may also be used. Other safe "water like"solvents, with low viscosity that can be used are 2-pyrrolidone, gammabutyrlactone and sulfolane.

Hygroscopic properties of the water like solvents of the above type aidsin the formation of the soft plug of ink in the orifice of the printhead of the ink jet printer. The soft plug means that there is a verythin layer formed in the orifice that can be easily broken upon firingof the print head. The additives, added to this ink formulations arepropylene glycol, n-butylether triethylene glycol butyl ether ordiethylene glycol ethers that are strong penetrants and thereforeimprove the speed of penetration into the paper and also the waterfastness of the prints. The long term solubility of the colorants in thesolvent system required for a long shelf life (more than 12 months) isachieved by adding non ionic surfactants. The non ionic surfactants canhave HLB from 8 to 13 in order to achieve solubilization ofpolyester/polyamide toner. The non ionic surfactants with HLB>8 are alsoless damaging to the plastic materials used in the printhead.

The general composition of the inks of this invention can be essentiallythe same as the composition of the fluorescent inks disclosed incopending U.S. patent application Ser. No. 08/570,140, Docket NumberE-407, entitled "Fluorescent Red And Magenta Waterfast Ink Jet Inks",filed herewith. The foregoing may be accomplished by using fluorescenttoners, which are commercially available and by increasing the opticaldensity and quenching the fluorescence completely with a high absorbancedye. The soluble toners without dyes (resins) containingdiemethyl-hydanton formaldehyde, polyester polyamide or triazineformaldehyde sulfonamide can be used in combinations with nonfluorescentdyes which are soluble in water. The preferred dyes are basic dyes withincreased water fastness. Various colors and hues may be obtained byusing the colored fluorescent toners: blue, green, red and then addingtrace to 8 (Wt. %) of dyes of the same hue as the toner which aresoluble in the solvent system. Black inks may be obtained by mixing thesubtractive colors, cyan, magenta and yellow toners. It will be obviousto one skilled in the art that any dye (not fluorescent) can be added tothe resin used in the ink formulations of this invention in order toobtain the desired color.

The general composition of the ink is as follows:

    ______________________________________                                        INGREDIENT                  (WT. %)                                           ______________________________________                                        1. Soluble toners            3-15                                             a. urea formaldehyde toluene sulfonamide                                      manufactured by Sterling 410 series mixtures                                  of magenta or yellow, or Day-Glo HMS series -                                 The resins used can be clear such as HM-35                                    or with dyes, such as HMS-30 and HMS-34                                       b. polyester polyamide (nonformaldehyde)                                      manufactured by Radiant ST series Magenta                                     and Yellow, or the Radiant ST clear (not containing dye)                      C. dimethyl hydantoin/formaldehyde manufactured by Lawter                     HVWT series magenta red or yellow, or HVWT - 10 clear                         (not containing dye).                                                         2. Dyes                     trace-1.5                                         a. C.I. Direct Yellow 86 manufactured by Daiwa or Aakash                      b. C.I. Direct Yellow, C.I. Basic Blue 7, C.I. Basic Blue 3,                  C.I. Basic Yellow 40                                                          c. any other dye soluble in water but preferably basic dyes                   3. Water                    35-55                                             4. Cosolvents as mixtures or individual solvents                                                          15-50                                             a. 2-pyrrolidone                                                              b. N-methyl pyrrolidone                                                       c. sulfolane                                                                  d. diethylene glycol                                                          e. gamma butyrlactone                                                         f. other solvents that will match the water like                              definition described herein                                                   5. Penetrants (glycol ether)                                                                               5-25                                             a. triethylene glycol N butyl ether                                           b. diethylene glycol N butyl ether                                            c. propylene glycol iso propyl ether                                          The following examples are exemplary of the invention and should not          be considered as limiting.                                                    6. Non ionic surfactants (optional)                                           a. nonyl phenoxy poly (ethyleneoxy) ethanol or                                b. decyl or tridecyl alcohol ethoxylates                                      ______________________________________                                    

EXAMPLE 1

    ______________________________________                                        Composition                                                                   Water                   47 wt %                                               2-Pyrrolidone           17 wt %                                               Polyethylene Glycol #200                                                                              10 wt %                                               Triethylene Glycol n Butyl Ether                                                                      10 wt %                                               Toner HVWT 54           15 wt %                                               from Lawter International                                                     C.I. Direct Yellow 142   1 wt %                                               Properties on Xerox 4024 Paper by Draw Down                                   Optical Density         0.73                                                  Hunter Color            L = 53 a = 34 b = 6                                   Waterfastness (after test)                                                    Optical Density         0.73                                                  Optical Density (bleeding part)                                                                       0.12                                                  ______________________________________                                        Print performance on various envelopes of example 1 ink by printhead          (20% duty).                                                                                 Print Performance                                               Envelope        OD     OD       OD   OD                                       Type            after water of bleeding part                                  ______________________________________                                        A - white wove, 24 lb.,                                                                       0.09   0.56     0.53 0.12                                     low ink absorbing                                                             B - white wove, 24 lb.,                                                                       0.09   0.57     0.51 0.11                                     high ink absorbing                                                            C - 24 lb. Smooth                                                                             0.09   0.53     0.49 0.12                                     finish                                                                        D - 24 lb. Classic                                                                            0.12   0.59     0.53 0.14                                     laid finish                                                                   E - 9 × 12                                                                              0.42   0.78     0.74 0.43                                     32 lb., 90 clasp                                                              F - Clay filled 0.07   0.55     0.55 0.07                                     paper stock                                                                   G - Calendared  0.05   0.53     0.53 0.07                                     paper stock                                                                   H- Air mail, #10                                                                              0.14   0.54     0.52 0.15                                     calendared matl.                                                              I - Recycled    0.09   0.61     0.57 0.11                                     paper stock                                                                   J - Tyvek       0.04   0.62     0.40 0.09                                     K - European    0.11   0.60     0.57 0.12                                     market, DL                                                                    ______________________________________                                    

EXAMPLE 2

    ______________________________________                                        Composition                                                                   Water                  45 wt %                                                2-Pyrrolidone          17 wt %                                                Polyethylene Glycol #200                                                                             10 wt %                                                Triethylene Glycol n Butyl Ether                                                                     10 wt %                                                Toner HVWT 10          15 wt %                                                from Lawter International                                                     C.I. Basic Blue 7       3 wt %                                                Properties on Xerox 4024 Paper by Draw Down                                   Optical Density        0.62                                                   Hunter Color           L = 37 a = 23 b = -79                                  Waterfastness (after dipping test)                                            Optical Density        0.62                                                   Optical Density (bleding part)                                                                       0.09                                                   ______________________________________                                    

EXAMPLE 3

    ______________________________________                                        Composition                                                                   Water                  47.5 wt %                                              2-Pyrrolidone          17 wt %                                                Polyethylene Glycol #200                                                                             10 wt %                                                Triethylene Glycol n Butyl Ether                                                                     10 wt %                                                Toner HVWT 54          7 wt %                                                 from Lawter International                                                     Toner HVWT 10          8 wt %                                                 from Lawter International                                                     C.I. Basic Blue 81     0.5 wt %                                               Properties on Xerox 4024 Paper by Draw Down                                   Optical Density        0.59                                                   Hunter Color           L = 44 a = 21 b = -59                                  Waterfastness (after dipping test)                                            Optical Density        0.57                                                   Optical Density (bleeding part)                                                                      0.09                                                   ______________________________________                                    

EXAMPLE 4

    ______________________________________                                        Composition                                                                   Water                  47.5 wt %                                              2-Pyrrolidone          17 wt %                                                Polyethylene Glycol #200                                                                             10 wt %                                                Triethylene Glycol n Butyl Ether                                                                     10 wt %                                                Toner HVWT 54          7 wt %                                                 from Lawter International                                                     Toner HWVT 10          8 wt %                                                 from Lawter International                                                     C. I. Basic Blue 3     0.5 wt %                                               Properties on Xerox 4024 Paper by Draw Down                                   Optical Density        0.55                                                   Hunter Color           L = 44 a = 12 b = -48                                  Waterfastness (after dipping test)                                            Optical bensity        0.54                                                   Optical Density (bleeding part)                                                                      0.09                                                   ______________________________________                                    

EXAMPLE 5

    ______________________________________                                        Composition                                                                   Water                  38 wt %                                                2-Pyrrolidone          45 wt %                                                Triethylene Glycol n Butyl Ether                                                                     12 wt %                                                Toner Flare 410 Magenta 37                                                                           3 wt %                                                 from Sterling                                                                 C.I. Basic Blue 7      2 wt %                                                 Properties on Xerox 4024 Paper by Draw Down                                   Optical Density        0.65                                                   Hunter Color           L = 32 a = 35 b = -70                                  Waterfastness (after dipping test)                                            Optical Density        0.65                                                   Optical Density (bleeding part)                                                                      0.09                                                   ______________________________________                                    

EXAMPLE 6

    ______________________________________                                        Composition                                                                   Water                  38 wt %                                                2-pyrrolidone          45 wt %                                                Triethylene Glycol n Butyl Ether                                                                     12 wt %                                                Toner HMS 30           3 wt %                                                 from Day Glo                                                                  C.I. Basic Blue 7      2 wt %                                                 Properties on Xerox 4024 Paper by Draw Down                                   Optical Density        0.64                                                   Hunter Color           L = 34 a = 34 b = -68                                  Waterfastness (after dipping test)                                            Optical Density        0.64                                                   Optical Density (bleeding part)                                                                      0.09                                                   ______________________________________                                    

EXAMPLE 7

    ______________________________________                                        Composition                                                                   Water                  38 wt %                                                2-Pyrrolidone          40 wt %                                                Triethylene Glycol n Butyl Ether                                                                     12 wt %                                                Toner ST Magenta       6 wt %                                                 from Radiant                                                                  C.I. Basic Blue 7      2 wt %                                                 Nonyl phenoxy poly (ethylene) ethanol                                                                2 wt %                                                 Properties on Xerox 4024 Paper by Draw Down                                   Optical Density        0.67                                                   Hunter Color           L = 31 a = 33 b = -65                                  Waterfastness (after dipping test)                                            Optical Density        0.67                                                   Optical Density (bleeding part)                                                                      0.09                                                   ______________________________________                                    

EXAMPLE 8

    ______________________________________                                        Composition                                                                   Water                  38 wt %                                                2-Pyrrolidone          45 wt %                                                Triethylene Glycol n Butyl Ether                                                                     12 wt %                                                Toner ST CR            3 wt %                                                 from Radiant                                                                  C.I. Basic Blue 7      2 wt %                                                 Properties on Xerox 4024 Paper by Draw Down                                   Optical Density        0.53                                                   Hunter Color           L = 38 a = 19 b = -78                                  Waterfastness (after dipping test)                                            Optical Density        0.53                                                   Optical Density (bleeding part)                                                                      0.09                                                   ______________________________________                                    

The above embodiments have been given by way of illustration only, andother embodiments of the instant invention will be apparent to thoseskilled in the art, from consideration of the detailed description.Accordingly, limitation on the instant invention are to be found only inthe claims.

What is claimed is:
 1. A postage metering system having a printingmechanism for printing postage, the improvement comprising: within theprinting mechanism employing an aqueous water-fast ink containing water,water soluble organic solvents, soluble toners and a glycol ether thatare inert to any plastic material contained in the printing mechanism.2. The system of claim 1, wherein the waterfast ink composition consistsessentially of:a. 35-55 (Wt. %) water; b. 15-50 (Wt. %) water solubleorganic solvents having a hydrogen bonding solubility parameter (δ_(h))greater than 8.0, a polar solubility parameter (δ_(p)) greater than 5.0and a dispersion parameter (δ.sub.δ) between 7-8.3; c. 3-15 (Wt. %)soluble toners with a molecular weight less than 6,000; d. trace-8.0(Wt. %) direct, acid, basic or reactive water soluble toning dye; and e.5-15 (Wt. %) of cosolvent penetrant.
 3. The system of claim 1, whereinthe waterfast ink composition consists essentially of:a. 35-55 (Wt. %)water; b. 15-47 (Wt. %) water soluble organic solvents having a hydrogenbonding solubility parameter (δ_(h)) greater than 5.0, a polarsolubility parameter (δ_(p)) between 8.0-8.7 and a dispersion parameter(δ.sub.δ) between 8.4-10.0; c. 3-15 (Wt. %) soluble toners with amolecular weight between 200 and a 1,000; d. trace-8.0 (Wt. %) direct,acid, basic or reactive water soluble toning dye; and e. 5-15 (Wt. %) ofcosolvent penetrant.
 4. The system of claim 1, wherein the waterfast inkcomposition consists essentially of:a. 35-55 (Wt. %) water; b. 5-25 (Wt.%) water soluble organic solvents having a hydrogen bonding solubilityparameter (δ_(h)) greater than 8.0, a polar solubility parameter (δ_(p))greater than 5.0 and a dispersion parameter (δ.sub.δ) between 7-8.3; c.5-25 (Wt. %) water soluble organic solvents having a hydrogen bondingsolubility parameter (δ_(h)) greater than 5.0, a polar solubilityparameter (δ_(p)) between 8.0-8.7 and a dispersion parameter (δ.sub.δ)between 8.4-10.0; d. 3-15 (Wt. %) soluble toners with a molecular weightbetween 200 and a 1,000; e. trace-8.0 (Wt. %) direct, acid, basic orreactive water soluble toning dye; and f. 5-15 (Wt. %) of cosolventpenetrant.
 5. A aqueous water fast ink composition consistingessentially of:a. 35-55 (Wt. %) water; b. 15-50 (Wt. %) water solubleorganic cosolvents having a hydrogen bonding solubility parameter(δ_(h)) greater than 8.0, a polar solubility parameter (δ_(p)) greaterthan 5.0 and a dispersion parameter (δ.sub.δ) between 7-8.3; c. 3-15(Wt. %) soluble toners with a molecular weight less than 6,000; d.trace-8.0 (Wt. %) direct, acid, basic or reactive water soluble toningdye; and e. 5-15 (Wt. %) of glycol ether as a cosolvent penetrant. 6.The composition claimed in claim 5, wherein the soluble toners have aweight average molecular weight between 300 and
 700. 7. The compositionclaimed in claim 6, wherein the, soluble toners contain non ionicsurfactants to increase the solubility of the ink.
 8. The compositionclaimed in claim 7, wherein the non ionic surfactant has an HLB between8 and
 15. 9. The composition claimed in claim 8, wherein the non ionicsurfactant is selected from the group consisting of: tridecyl alcoholethoxylates and nonyl phenoxy poly (ethyleneoxy) ethoxylates.
 10. Thecomposition claimed in claim 5, wherein the soluble toners arefluorescent toners.
 11. The composition of claim 5, wherein the toningdye is selected from the group consisting of C.I. Direct Yellow 86, C.I.Acid Yellow 210, C.I. Basic Yellow, 40, C.I. Basic Yellow 51, C.I. BasicYellow
 2. 12. The composition claimed in claim 5, wherein the solubletoners are clear toners.
 13. The composition of claim 1, wherein theglycol ethers have a viscosity of less than 20 cps.
 14. The compositionof claim 5, wherein the soluble toner is selected from the groupconsisting of urea formaldehyde toluene sulfonamide, polyester-polyamideor dimethyl hydantoin formaldehyde.
 15. The composition of claim 1,wherein the polyester polyamide soluble toner has an acid number greaterthan
 50. 16. The composition of claim 5, wherein the water solubleorganic solvents individually or in solution do not exceed a viscosityof 20 cps.
 17. The composition of claim 16, wherein the water solubleorganic solvents have a vapor pressure less than 0.1 mm/Hg at roomtemperature.
 18. The composition claimed in claim 5, wherein the watersoluble organic solvents are selected from the group consisting of:pyrrolidone, N-methyl pyrrolidone or triethylene glycol.
 19. Thecomposition of claim 7, wherein the toning dye is selected from thegroup consisting of: Basic Yellow 40, Basic Yellow 51, Basic Blue 7,Basic Blue 3 and C.I. Direct Yellow
 142. 20. A aqueous water fast inkcomposition consisting essentiallya. 35-55 (Wt. %) water; b. 15-47 (Wt.%) water soluble organic solvents having a hydrogen bonding solubilityparameter (δ_(h)) greater than 5.0, a polar solubility parameter (δ_(p))between 8.0-8.7 and a dispersion parameter (δ.sub.δ) between 8.4-10.0;c. 3-15 (Wt. %) soluble toners with a molecular weight between 200 and a1,000; d. trace-8.0 (Wt. %) direct, acid, basic or reactive watersoluble toning dye; and e. 5-15 (Wt. %) of glycol ether as a cosolventpenetrant.
 21. The composition claimed in claim 20, wherein the solubletoners contain non ionic surfactants to increase the solubility of theink.
 22. The composition claimed in claim 21, wherein the non ionicsurfactant has an HLB between 8 and
 15. 23. The composition claimed inclaim 22, wherein the non ionic surfactant is selected from the groupconsisting of: tridecyl alcohol alkoxylates and nonyl phenoxy polyoxyethylene alcohols.
 24. The composition claimed in claim 23, wherein thenon ionic surfactant is used at concentrations from trace to 3 Wt. %.25. The composition claimed in claim 20, wherein the soluble toners arefluorescent toners.
 26. The composition claimed in claim 20, wherein thesoluble toners are clear toners.
 27. The composition of claim 25,wherein the fluorescent toner is selected from the group consisting ofurea formaldehyde toluene sulfonamide, polyester polyamide or dimethylhydantoin formaldehyde.
 28. The composition of claim 20, wherein thewater soluble organic solvents are selected from the group consisting of2-Pyrrolidone, N-methyl pyrrolidone, sulfolane, and gamma butyrlactone.29. The composition of claim 16, wherein the toning dye is selected fromthe group consisting of: Basic Yellow 40, Basic Yellow 51, Basic Blue 7,Basic Blue 3 and C.I. Direct Yellow
 142. 30. A aqueous water fast inkcomposition consisting essentially of:a. 35-55 (Wt. %) water; b. 5-25(Wt. %) water soluble organic solvents having a hydrogen bondingsolubility parameter (δ_(h)) greater than 8.0, a polar solubilityparameter (δ_(p)) greater than 5.0 and a dispersion parameter (δ.sub.δ)between 7-8.3; c. 5-25 (Wt. %) water soluble organic solvents having ahydrogen bonding solubility parameter (δ_(h)) greater than 5.0, a polarsolubility parameter (δ_(p)) between 8.0-8.7 and a dispersion parameter(δ.sub.δ) between 8.4-10.0; d. 3-15 (Wt. %) soluble toners with amolecular weight between 200 and a 1,000; e. trace-8.0 (Wt. %) direct,acid, basic or reactive water soluble toning dye; and f. 5-15 (Wt. %) ofglycol ether as a cosolvent penetrant.